The drug, Vyvanse, is usually used for ADHD but it's been shown to help control binge-eating disorder, the FDA said.

"In binge-eating disorder, patients have recurrent episodes of compulsive overeating during which they consume larger amounts of food than normal and experience the sense that they lack control. Patients with this condition eat when they are not hungry and often eat to the point of being uncomfortably full," the FDA said in a statement.

"Patients may feel ashamed and embarrassed by how much they are eating, which can result in social isolation. Binge-eating disorder may lead to weight gain and to health problems related to obesity."

The drug is not approved for weight loss, and it's a Schedule II controlled substance because it has high potential for abuse and dependence. But any doctor can write a prescription for any approved drug for any use he or she sees fit.

"The concern in our country especially is the desperation to lose weight," said NBC's diet and nutrition editor Madelyn Fernstrom. "Everyone will say, 'Oh, I have binge eating disorder'. I think there's a huge potential for abuse in our country."